NL8602671A - METHOD FOR POLYMERIZING AN UNSATURATED COMPOUND IN A MOLD - Google Patents

Description

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Process for polymerizing an unsaturated compound in a mold

The present invention relates to a method of polymerizing an unsaturated compound having a vinyl or vinylidene group (hereinafter referred to as "vinyl type monomer") in a mold. More particularly, the invention relates to a method of polymerizing a vinyl type monomer in a mold, comprising specifically mixing the vinyl type monomer optionally containing its polymer with a polymerization initiator and a polymerization accelerator , and rapid polymerization and molding in the mold, for producing a molded article with good efficiency.

Generally, a vinyl or vinylidene polymer (hereinafter referred to as "vinyl type polymer") is cast by melt casting, for example, injection molding, comprising melting a polymer in the form of a powder, spheres, or granules at a high temperature, and injecting the molten polymer into a mold.

For manufacturing sheet material of polymethyl methacrylate, a cell casting process is known which includes pouring methyl methacrylate optionally containing its polymer into a glass plate cell and gradually polymerizing the methyl methacrylate over a long period of time, for example for a number of hours, as well as a continuous casting process comprising casting an unsaturated monomer comprising a polymer-containing methyl methacrylate on an endless metal belt, and polymerizing it for a comparatively short period of time (see Japanese Patent Publication No. 30985 1977 and 35393/1977).

If the vinyl type polymer is melt-cast, for example, injection molding, it must be cast in a narrow temperature range, in which the polymer has melted 8602671 "4 - 2 - * but not thermally decomposed, because the polymer tends to thermally decompose at high temperature and pressure required for melt molding Therefore, melt molding of the vinyl type polymer requires a large amount of energy and a large-scale, complicated device In addition, the molten vinyl type polymer has a very high viscosity even at high temperature, so that much knowledge is required for the precisely transfer the surface images from the mold to the molded object.

Except for the casting of plate-shaped objects, cell casting is not widely used, because the polymerization rate cannot be increased in this process, leading to poor productivity. Although continuous casting has good productivity, an expensive device is required that can manufacture only a plate-shaped object.

In these conventional processes, all components, including the monomer and the polymerization initiator, are mixed together and poured into the reaction cavity for the polymerization of the monomer. In such a case, if a polymerization initiator yields a high polymerization rate, the polymerization reaction will not proceed homogeneously.

An object of the present invention is to provide a method of providing accurately shaped vinyl type polymer articles with good efficiency using a comparatively small amount of energy and a comparatively simple device.

Another object of the present invention is to provide a process for a rapid mold-polymerization of the vinyl type monomer.

These and other objects are accomplished by a mold polymerizing method of a vinyl type 35 monomer comprising mixing the monomer compound containing a polymerization initiator with a monomer compound comprising a polymerization accelerator, mixing 8602671 - 3 - of the mixture in a mold cavity, and polymerizing the monomer for a period of not more than 30 minutes.

Examples of the vinyl type monomer that can be polymerized by the process of the invention are a methacrylate or acrylate of a C 1 -C 25 straight, alicyclic or aromatic alcohol or phenol (eg methyl methacrylate, ethyl methacrylate, butyl methacrylate, phenyl methacrylate, benzyl methacrylate, cyclohexylmethacryl 10 late, bornyl methacrylate, isobornyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, phenyl acrylate, benzyl acrylate, cyclohexyl acrylate, bornyl acrylate, and isobornyl acrylate); vinyl nitriles (e.g., acrylonitrile, methacrylonitrile and crotonitrile)? vinyl esters (eg vinyl acetate, vinyl propionate and vinyl benzoate); methacrylic acid and acrylic acid. Methacrylates are preferred because of their good reactivity.

Although the monomer can be used per se, it can also be used as a mixture with at least one of the other monomers in order to improve the characteristics of the polymer produced and / or to increase the reactivity of the monomers.

In addition, at least one of the other copolymerizable monomers, such as styrene, methyl methyl styrene, p-methyl styrene, maleic anhydride and the like, can be used in conjunction with the above monomer (s).

Although the monomer can be polymerized as such, it is advantageous to polymerize the monomer containing its polymer, namely a so-called "syrup", due to the improvement of the polymerization activity and ease of handling. the polymer in the syrup is usually from 3 to 40% by weight If the polymer content in the syrup exceeds 40% by weight, the syrup has too high a viscosity, so that the handling of the syrup is counteracted.

The syrup can be prepared by a customary method per se. For example, polymerization of the monomer is initiated by adding a polymerization initiator and terminated when the conversion has reached a certain level, or an adequate amount of the polymer has dissolved in the monomer.

As a polymerization initiator, a radical polymerization initiator is preferably used, although other initiators can be used. Of these, radical initiators of the peroxide type are preferred. In view of the stability of the monomer containing the polymerization initiator and optionally the polymer, it is advantageous to use an initiator with a half-life of 10 hours at a temperature not lower than 50 ° C and preferably not lower than 60 ° C. Examples of a radical polymerization initiator are dialkyl peroxides (e.g. di-t-butyl-15 peroxide, t-butyl cumyl peroxide and dicumyl peroxide); diacyl peroxide (e.g. lauroyl peroxide, benzoyl peroxide and succinic acid peroxide); peroxyesters (e.g. t-butyl peroxyacetate, t-butylperoxybenzoate, t-butylperoxy pivalate and t-butylperoxylaurate) y hydroperoxides (e.g. t-butylhydroperoxide and cumene hydroperoxide); and ketone peroxides (e.g., methyl ethyl ketone peroxide), and mixtures thereof.

The amount of initiator is from 0.05 to 5 parts by weight, preferably from 0.5 to 2 parts by weight per 100 parts by weight of monomer optionally containing its polymer.

If the amount of initiator is less than 0.05 parts by weight, the polymerization will not proceed completely. If it exceeds 5 parts by weight, polymerization control is difficult and the polymer produced has poor weather and heat resistance.

As a polymerization accelerator, a compound is preferably used which decomposes the polymerization initiator and accelerates the formation of radicals, such as a reducing agent.

As the reducing agent, a compound is used which is soluble in the vinyl type monomer, for example mono-, di-, tri- or tetravalent sulfur compounds, such as sulfinates (eg methyl-p-toluenesulfinate and ethyl-p-toluenesulfon-8602671 r). 5-trinates), thiourea (e.g. tetramethylthiourea and dibutyl thiourea), mercaptans (e.g. lauryl mercaptan, t-dodecyl mercaptan, octyl mercaptan, butyl mercaptan, 2-ethylhexyl mercaptan, 2-ethylhexyl thioglycol tetraethyl ether) glycol dimercaptoacetate, 2-mercaptoethanol and its esters, β-mercaptopropionic acid and its esters); tertiary amines (e.g. N, N-dimethylaniline, N, N-dimethyl-p-toluidine and N, N-di- (2-hydroxypropyl) -p-toluidine); trivalent phosphorus compounds, such as phosphites (e.g. trimethyl-10 phosphite, triethyl phosphite and tri-n-butyl phosphite) and the like.

The reducing agent is used in an amount from 0.05 to 5 parts by weight, preferably 0.5-2 parts by weight, per 100 parts by weight of monomer optionally containing the polymer. When it is used in an amount less than 0.05 parts by weight, the polymerization rate is not accelerated sufficiently. If it exceeds 5 parts by weight, the polymer prepared is colored and / or its strength is deteriorated.

As an additional component for the polymerization accelerator, a heavy metal-containing compound and a hydrogen halide salt of an amine or a quaternary ammonium halide can be used. These compounds further accelerate the polymerization reaction.

As the heavy metal-containing compound, there can be exemplified a compound having at least one metal selected from the group consisting of iron, copper and cobalt, which is soluble in the vinyl type monomer. Specific examples are naphthenates and acetylacetonates of these metals.

The amount of the heavy metal containing compound to be added is 0.005 to 10 ppm, preferably 0.1 to 5 ppm in terms of amount of metal per unit weight of vinyl type monomer. If the amount is less than 0.005 ppm, the polymerization is not actually accelerated. If it is greater than 10 ppm, the polymerization initiator is inactivated, so that the polymerization is blocked.

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As the hydrogen halide salt of an amine or the quaternary ammonium halide, examples are hydrogen chloride salts and hydrogen bromide salts of amines (e.g. n-amylamine, n-hexylamine, n-octylamine, n-decylamine, lauryl-5 amine, palmitylamine, dibutylamine, tributylamine N, N-dimethylbenzylamine, N, N-dimethyl-p-toluidine, phenethyldi-butylamine, N, N, N ', N'-tetrarnethylhexamethylenediamine, N, N, N', N1-tetramethylpropyldiamine, N, N-diethylbenzylamine , Ν, Ν-dibutylbenzylamine and phenethyldiethylamine); and tetra-10 methyl ammonium chloride, benzyl trimethyl ammonium chloride, benzyl triethyl ammonium chloride, benzyl tributyl ammonium chloride, trioctyl methyl ammonium chloride, and phenethyl dibutyl ethoxycarbonyl methyl ammonium chloride. These compounds can be used in an amount from 0.005 to 15 parts by weight, preferably 0.01 to 0.5 parts by weight, per 100 parts by weight of the vinyl monomer optionally containing the polymer. If the amount is less than 0.005 parts by weight or greater than 1 part by weight, the polymerization is not effectively accelerated.

These compounds can be used per se if they are soluble in the monomer, or in the form of a solution in a suitable solvent (eg, isopropanol, dimethyl phthalate, diethylene glycol and the like) if it is insoluble in the monomer.

In accordance with the present invention, the monomer containing the polymerization initiator and optionally the corresponding polymer, and the monomer containing the polymerization accelerator are mixed to initiate the polymerization.

For rapid advancement and completion of the polymerization of the vinyl type monomer, an initiator and other additives with a high polymerization activity are used. Therefore, when the initiator and the other additives are added separately to the same porous monomer, it can sometimes be difficult to mix them uniformly over a short period of time and to allow the polymerization reaction to proceed homogeneously.

8602671 * t y - 7 -

According to the method of the present invention, the monomer and additional components containing the polymerization initiator and the like are homogeneously mixed in a short time so that the reaction proceeds homogeneously. The additional polymerization accelerator components are added to one of the two monomer portions.

Mixing of the two monomer portions is preferably performed for 10 minutes or less at a temperature not higher than 50oC.

If the mixing temperature is above 50 ° C, the polymerization is unfavorably initiated in part and proceeds during mixing. If the mixing time is too long, the polymerization proceeds during mixing and pouring.

The mixing time should be as short as possible to thoroughly mix the monomer portions.

In the case of casting a small object, the monomer portions can be mixed batchwise and poured into the mold cavity. This operation is not suitable for casting a large object. Preferably, the monomer portions are continuously mixed and poured into the mold cavity, because the monomer and the additives are homogeneously mixed and a large article can be manufactured. In any case, the mixing time for the monomer in order to pour it into the mold cavity should be as short as possible.

The mixing can be carried out according to a method known per se, for instance with the aid of a collision-type mixer, a dynamic mixer and a static mixer.

Compared to the conventional molding method in which a molten resin is poured into the mold cavity, the method of the present invention requires relatively low injection pressure, because the vinyl type monomer used as casting material has a lower viscosity than the molten resin. Therefore, the volume of the mold cavity can vary from small to large. The mold can be made of metal, resin, elastomer or wood. Of these 8602671 - 8 - a metal mold is preferred because of its accuracy and durability.

The temperature of the mold can be controlled with a heating unit embedded in the mold wall, air cooling, or a jacket, or a conduit fitted in the mold wall, through which a heat exchanging medium such as water or oil is passed .

The polymerization time in the process of the invention varies depending on the type and amount of the polymerization initiator and / or other additives, the mold temperature and the like, and is usually no more than 30 minutes, preferably no more than 15 minutes, more preferably no longer than 10 minutes.

The method of the invention can be used to manufacture any molded article made from the vinyl type polymer. That is, by changing the shape and size of the mold cavity, any molded article can be manufactured according to the method of the invention.

In particular, the method according to the invention is suitable for manufacturing optical components, because the shaped object has a considerably smaller internal tension. The optical components include conventional lenses, Fresnel lenses, media for the optical recording on discs, prisms and mirrors.

Of these, Fresnel lenses which must have an accurate shape are preferably manufactured according to the method according to the invention, because the precise image of the mold can be transferred to the polymer manufactured according to the invention.

Since a large-sized object can also be formed by the method of the invention, auto parts, such as a windshield plate, a sunroof, a side window and a rear window, a dashboard, a water tank panel, and a bathtub manufactured.

In accordance with the present invention, the vinyl type polymer can be formed at a much lower temperature and 8602671 c-9 pressure than in the conventional methods, and the surface image of the mold cavity can be accurately transferred to the molded object much more easily than in the conventional methods. In addition, the vinyl-type polymer molded article 5 can be manufactured in a shorter time than in a conventional casting polymerization process.

Examples

Current and practical preferred embodiments of the present invention will be illustrated by the following examples, wherein haze value and Rockwell hardness, respectively. are measured according to ASTM D 790 and ASTM D 785.

Example 1 Preparation of a Raw Syrup

To a stainless steel vessel, methyl methacrylate resin (SUMIPEX (trademark) B MH manufactured by Sumitomo Chemical) (2 kg) and methyl methacrylate monomer (8 kg) were added and stirred for 24 hours to prepare a crude syrup that was a viscous liquid with a viscosity of one poise.

Preparation of Syrup A.

In the crude syrup (1000 g) filled into a 2 liter stainless steel vessel, an 8 wt% solution of dibutylamine hydrochloride in diethylene glycol (12.5 g) and t-butyl peroxybenzoate (10 g ) added and dissolved to make Stroop A.

Preparation of Stroop B

2-Mercaptoethanol (4 g) and a 1 wt.% Solution of copper naphthenate (Cu content 10%) in methyl methacrylate (in the crude syrup (1000 g), which was filled in a 2 liter stainless steel vessel) 0.4 g) mixed and dissolved to prepare Stroop B.

When storing Stroop A and B at room temperature (25eC), their viscosities were essentially unchanged and remained within a useful limit the day after.

Stroop A (300 g) and Stroop B (300 g) were pumped into a dynamic mixer and mixed at room temperature (25 ° C) with an average mixing time of 30 sec. Then the mixture was poured into a mold (350 x 350 x 3 mm) which was kept at 55 ° C. 6.8 minutes after the completion of the pouring, the polymerization temperature became maximum. After 8 minutes, the molded polymer was removed from the mold to yield a molded article having a haze value of 1.0%, a Rockwell hardness of 97 (M scale) as well as good gloss.

10 Example 2

Stroop A (300 g) and Stroop B (300 g) prepared in Example 1 were fed from two tanks at the same speed to the mixer with an average mixing time of 2 minutes. The mixture was poured directly into a mold 15 (350 x 350 x 4mm) which was kept at 85 ° C. 2 minutes after the completion of the pouring, the mold containing the mixture was cooled to yield polymethyl methacrylate, which was homogeneous and transparent and had good surface hardness and glass.

20 Example 3

Preparation of a Raw Syrup

Methyl methacrylate (560 g), methyl acrylate (140 g) and azobisisobutylonitrile (0.07 g) were added to a reactor and partially polymerized with gentle stirring at 80 ° C. After the viscosity of the reaction mixture reached about one poise, the vessel was cooled with ice water to yield a crude syrup with a viscosity of 2 poise.

Preparation of Stroop A '30 In the crude syrup (300 g) filled into a 500 ml glass flask, ethylene glycol dimethacrylate (9 g) and benzoyl peroxide (12 g) were added and dissolved to yield Stroop A'.

Preparation of Syrup B '35 In the crude syrup (300 g) filled into a 500 ml glass flask, ethylene glycol dimethacrylate (9 g), 2-ethylhexyl thioglycolate (0.3 g) and N, N-dimethylaniline 8602671 * -lice g) added and dissolved to yield Stroop B '.

Syrup A 'and B * were fed to and mixed in a mixer with an average mixing time of 30 sec. Then the mixture was poured into a mold (350 x 350 x 54mm) which was kept at 80 ° C. The polymerization temperature reached maximum 4 minutes after the completion of the pouring. 8 minutes after the completion of the pouring, the polymer was removed from the mold to yield a molded article which had no bubbles but with a good gloss, haze-10 value of 1.2% and a Rockwell hardness of 97 (M scale) .

Comparative example 1

The following components were thoroughly mixed:

Crude syrup from example 1 600 g t-butylperoxybenzoate 3 g 15 dibutylamine hydrochloride 0.3 g diethylene glycol 3 g 2-mercaptoethanol 1.2 g copper naphthenate (Cu ^ +, 10%) 0.001 g

The mixture was poured into a mold (350 x 350 x 20 3mm) kept at 85 ° C. The polymer produced was inhomogeneously translucent and had many bubbles.

The remaining mixture had poor storage properties, so that after 60 minutes it polymerized under vigorous heat development at room temperature (25 ° C).

25 8602671

Claims (7)

1. A method for polymerizing an unsaturated compound with a vinyl or vinylidene group in a mold, comprising mixing the unsaturated compound containing a polymerization initiator and an unsaturated compound containing a polymerization accelerator, pouring a mold cavity from the mixture, and polymerizing the monomer for a period of no more than 30 minutes. 2. A method according to claim 1, characterized in that the mixing of the two portions of unsaturated compounds and pouring the mixture into the mold are carried out continuously. Method according to claim 1 or 2, characterized in that the unsaturated compound comprises at least one methacrylate or acrylate. Method according to claims 1-3, characterized in that the mold is kept at a temperature between 50 and 150 ° C. 5. Process according to claims 1-4, characterized in that the polymerization initiator is a radical polymerization initiator of the peroxide type, and the polymerization accelerator is a reducing agent. A method according to claims 1 to 5, characterized in that the unsaturated compound contains its polymer. 25 Process according to claims 1-6, characterized in that the polymer content in the unsaturated compound is from 3 to 40% by weight. 8602671